Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

bolt patterns

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Old 03-16-07, 03:28 PM
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trebor
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bolt patterns

hello everyone i'm new to this site and to riding in general and have a couple of quick questions i was given an older late 70's or early 80's norco with freewheel which i have converted to a fixie but was wondering about the differences in b.c.d. and if there is a difference in riding or performance and why do they have different sizes i see 110 130 144 ? i have 165 cranks if that makes a difference any help would be appreciated
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Old 03-16-07, 03:32 PM
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mihlbach
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Well, a smaller BCD allows you to run really small chainrings, which is why mtb cranks have a small bcd. On the other hand, I suppose if you are running a larger chainring, a larger diameter BCD probably results in a stiffer drivetrain. 130 is a good all around bcd, which allows you to run small and large chainrings and is typical for roadbikes. Track bcd is larger, generally 144, because only large chainrings with tooth counts ranging from the upper 40s to lower 50s are used on the track.

BCD is unrelated to your crank length. I wouldn't worry to much about bcd specifically. The gear ratio is more important, as long as you can find a chainring to fit your cranks (with the same bcd) that puts you in the range of gearing that you want you will be fine.

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Old 03-16-07, 03:34 PM
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http://sheldonbrown.com/gloss_bo-z.html#bcd
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Old 03-16-07, 03:41 PM
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thanks guys i appreciate the response cheers
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